Mauro Carvalho Chehab | 8e080c2 | 2009-09-13 22:16:04 -0300 | [diff] [blame] | 1 | <refentry id="vidioc-dbg-g-register"> |
| 2 | <refmeta> |
| 3 | <refentrytitle>ioctl VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER</refentrytitle> |
| 4 | &manvol; |
| 5 | </refmeta> |
| 6 | |
| 7 | <refnamediv> |
| 8 | <refname>VIDIOC_DBG_G_REGISTER</refname> |
| 9 | <refname>VIDIOC_DBG_S_REGISTER</refname> |
| 10 | <refpurpose>Read or write hardware registers</refpurpose> |
| 11 | </refnamediv> |
| 12 | |
| 13 | <refsynopsisdiv> |
| 14 | <funcsynopsis> |
| 15 | <funcprototype> |
| 16 | <funcdef>int <function>ioctl</function></funcdef> |
| 17 | <paramdef>int <parameter>fd</parameter></paramdef> |
| 18 | <paramdef>int <parameter>request</parameter></paramdef> |
| 19 | <paramdef>struct v4l2_dbg_register *<parameter>argp</parameter></paramdef> |
| 20 | </funcprototype> |
| 21 | </funcsynopsis> |
| 22 | <funcsynopsis> |
| 23 | <funcprototype> |
| 24 | <funcdef>int <function>ioctl</function></funcdef> |
| 25 | <paramdef>int <parameter>fd</parameter></paramdef> |
| 26 | <paramdef>int <parameter>request</parameter></paramdef> |
| 27 | <paramdef>const struct v4l2_dbg_register |
| 28 | *<parameter>argp</parameter></paramdef> |
| 29 | </funcprototype> |
| 30 | </funcsynopsis> |
| 31 | </refsynopsisdiv> |
| 32 | |
| 33 | <refsect1> |
| 34 | <title>Arguments</title> |
| 35 | |
| 36 | <variablelist> |
| 37 | <varlistentry> |
| 38 | <term><parameter>fd</parameter></term> |
| 39 | <listitem> |
| 40 | <para>&fd;</para> |
| 41 | </listitem> |
| 42 | </varlistentry> |
| 43 | <varlistentry> |
| 44 | <term><parameter>request</parameter></term> |
| 45 | <listitem> |
| 46 | <para>VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER</para> |
| 47 | </listitem> |
| 48 | </varlistentry> |
| 49 | <varlistentry> |
| 50 | <term><parameter>argp</parameter></term> |
| 51 | <listitem> |
| 52 | <para></para> |
| 53 | </listitem> |
| 54 | </varlistentry> |
| 55 | </variablelist> |
| 56 | </refsect1> |
| 57 | |
| 58 | <refsect1> |
| 59 | <title>Description</title> |
| 60 | |
| 61 | <note> |
| 62 | <title>Experimental</title> |
| 63 | |
| 64 | <para>This is an <link linkend="experimental">experimental</link> |
| 65 | interface and may change in the future.</para> |
| 66 | </note> |
| 67 | |
| 68 | <para>For driver debugging purposes these ioctls allow test |
| 69 | applications to access hardware registers directly. Regular |
| 70 | applications must not use them.</para> |
| 71 | |
| 72 | <para>Since writing or even reading registers can jeopardize the |
| 73 | system security, its stability and damage the hardware, both ioctls |
| 74 | require superuser privileges. Additionally the Linux kernel must be |
| 75 | compiled with the <constant>CONFIG_VIDEO_ADV_DEBUG</constant> option |
| 76 | to enable these ioctls.</para> |
| 77 | |
| 78 | <para>To write a register applications must initialize all fields |
| 79 | of a &v4l2-dbg-register; and call |
| 80 | <constant>VIDIOC_DBG_S_REGISTER</constant> with a pointer to this |
| 81 | structure. The <structfield>match.type</structfield> and |
| 82 | <structfield>match.addr</structfield> or <structfield>match.name</structfield> |
| 83 | fields select a chip on the TV |
| 84 | card, the <structfield>reg</structfield> field specifies a register |
| 85 | number and the <structfield>val</structfield> field the value to be |
| 86 | written into the register.</para> |
| 87 | |
| 88 | <para>To read a register applications must initialize the |
| 89 | <structfield>match.type</structfield>, |
| 90 | <structfield>match.chip</structfield> or <structfield>match.name</structfield> and |
| 91 | <structfield>reg</structfield> fields, and call |
| 92 | <constant>VIDIOC_DBG_G_REGISTER</constant> with a pointer to this |
| 93 | structure. On success the driver stores the register value in the |
| 94 | <structfield>val</structfield> field. On failure the structure remains |
| 95 | unchanged.</para> |
| 96 | |
| 97 | <para>When <structfield>match.type</structfield> is |
| 98 | <constant>V4L2_CHIP_MATCH_HOST</constant>, |
| 99 | <structfield>match.addr</structfield> selects the nth non-&i2c; chip |
| 100 | on the TV card. The number zero always selects the host chip, ⪚ the |
| 101 | chip connected to the PCI or USB bus. You can find out which chips are |
| 102 | present with the &VIDIOC-DBG-G-CHIP-IDENT; ioctl.</para> |
| 103 | |
| 104 | <para>When <structfield>match.type</structfield> is |
| 105 | <constant>V4L2_CHIP_MATCH_I2C_DRIVER</constant>, |
| 106 | <structfield>match.name</structfield> contains the I2C driver name. |
| 107 | For instance |
| 108 | <constant>"saa7127"</constant> will match any chip |
| 109 | supported by the saa7127 driver, regardless of its &i2c; bus address. |
| 110 | When multiple chips supported by the same driver are present, the |
| 111 | effect of these ioctls is undefined. Again with the |
| 112 | &VIDIOC-DBG-G-CHIP-IDENT; ioctl you can find out which &i2c; chips are |
| 113 | present.</para> |
| 114 | |
| 115 | <para>When <structfield>match.type</structfield> is |
| 116 | <constant>V4L2_CHIP_MATCH_I2C_ADDR</constant>, |
| 117 | <structfield>match.addr</structfield> selects a chip by its 7 bit &i2c; |
| 118 | bus address.</para> |
| 119 | |
| 120 | <para>When <structfield>match.type</structfield> is |
| 121 | <constant>V4L2_CHIP_MATCH_AC97</constant>, |
| 122 | <structfield>match.addr</structfield> selects the nth AC97 chip |
| 123 | on the TV card.</para> |
| 124 | |
| 125 | <note> |
| 126 | <title>Success not guaranteed</title> |
| 127 | |
| 128 | <para>Due to a flaw in the Linux &i2c; bus driver these ioctls may |
| 129 | return successfully without actually reading or writing a register. To |
| 130 | catch the most likely failure we recommend a &VIDIOC-DBG-G-CHIP-IDENT; |
| 131 | call confirming the presence of the selected &i2c; chip.</para> |
| 132 | </note> |
| 133 | |
| 134 | <para>These ioctls are optional, not all drivers may support them. |
| 135 | However when a driver supports these ioctls it must also support |
| 136 | &VIDIOC-DBG-G-CHIP-IDENT;. Conversely it may support |
| 137 | <constant>VIDIOC_DBG_G_CHIP_IDENT</constant> but not these ioctls.</para> |
| 138 | |
| 139 | <para><constant>VIDIOC_DBG_G_REGISTER</constant> and |
| 140 | <constant>VIDIOC_DBG_S_REGISTER</constant> were introduced in Linux |
| 141 | 2.6.21, but their API was changed to the one described here in kernel 2.6.29.</para> |
| 142 | |
| 143 | <para>We recommended the <application>v4l2-dbg</application> |
| 144 | utility over calling these ioctls directly. It is available from the |
| 145 | LinuxTV v4l-dvb repository; see <ulink |
| 146 | url="http://linuxtv.org/repo/">http://linuxtv.org/repo/</ulink> for |
| 147 | access instructions.</para> |
| 148 | |
| 149 | <!-- Note for convenience vidioc-dbg-g-chip-ident.sgml |
| 150 | contains a duplicate of this table. --> |
| 151 | <table pgwide="1" frame="none" id="v4l2-dbg-match"> |
| 152 | <title>struct <structname>v4l2_dbg_match</structname></title> |
| 153 | <tgroup cols="4"> |
| 154 | &cs-ustr; |
| 155 | <tbody valign="top"> |
| 156 | <row> |
| 157 | <entry>__u32</entry> |
| 158 | <entry><structfield>type</structfield></entry> |
| 159 | <entry>See <xref linkend="ident-chip-match-types" /> for a list of |
| 160 | possible types.</entry> |
| 161 | </row> |
| 162 | <row> |
| 163 | <entry>union</entry> |
| 164 | <entry>(anonymous)</entry> |
| 165 | </row> |
| 166 | <row> |
| 167 | <entry></entry> |
| 168 | <entry>__u32</entry> |
| 169 | <entry><structfield>addr</structfield></entry> |
| 170 | <entry>Match a chip by this number, interpreted according |
| 171 | to the <structfield>type</structfield> field.</entry> |
| 172 | </row> |
| 173 | <row> |
| 174 | <entry></entry> |
| 175 | <entry>char</entry> |
| 176 | <entry><structfield>name[32]</structfield></entry> |
| 177 | <entry>Match a chip by this name, interpreted according |
| 178 | to the <structfield>type</structfield> field.</entry> |
| 179 | </row> |
| 180 | </tbody> |
| 181 | </tgroup> |
| 182 | </table> |
| 183 | |
| 184 | |
| 185 | <table pgwide="1" frame="none" id="v4l2-dbg-register"> |
| 186 | <title>struct <structname>v4l2_dbg_register</structname></title> |
| 187 | <tgroup cols="4"> |
| 188 | <colspec colname="c1" /> |
| 189 | <colspec colname="c2" /> |
| 190 | <colspec colname="c4" /> |
| 191 | <tbody valign="top"> |
| 192 | <row> |
| 193 | <entry>struct v4l2_dbg_match</entry> |
| 194 | <entry><structfield>match</structfield></entry> |
| 195 | <entry>How to match the chip, see <xref linkend="v4l2-dbg-match" />.</entry> |
| 196 | </row> |
| 197 | <row> |
| 198 | <entry>__u64</entry> |
| 199 | <entry><structfield>reg</structfield></entry> |
| 200 | <entry>A register number.</entry> |
| 201 | </row> |
| 202 | <row> |
| 203 | <entry>__u64</entry> |
| 204 | <entry><structfield>val</structfield></entry> |
| 205 | <entry>The value read from, or to be written into the |
| 206 | register.</entry> |
| 207 | </row> |
| 208 | </tbody> |
| 209 | </tgroup> |
| 210 | </table> |
| 211 | |
| 212 | <!-- Note for convenience vidioc-dbg-g-chip-ident.sgml |
| 213 | contains a duplicate of this table. --> |
| 214 | <table pgwide="1" frame="none" id="chip-match-types"> |
| 215 | <title>Chip Match Types</title> |
| 216 | <tgroup cols="3"> |
| 217 | &cs-def; |
| 218 | <tbody valign="top"> |
| 219 | <row> |
| 220 | <entry><constant>V4L2_CHIP_MATCH_HOST</constant></entry> |
| 221 | <entry>0</entry> |
| 222 | <entry>Match the nth chip on the card, zero for the |
| 223 | host chip. Does not match &i2c; chips.</entry> |
| 224 | </row> |
| 225 | <row> |
| 226 | <entry><constant>V4L2_CHIP_MATCH_I2C_DRIVER</constant></entry> |
| 227 | <entry>1</entry> |
| 228 | <entry>Match an &i2c; chip by its driver name.</entry> |
| 229 | </row> |
| 230 | <row> |
| 231 | <entry><constant>V4L2_CHIP_MATCH_I2C_ADDR</constant></entry> |
| 232 | <entry>2</entry> |
| 233 | <entry>Match a chip by its 7 bit &i2c; bus address.</entry> |
| 234 | </row> |
| 235 | <row> |
| 236 | <entry><constant>V4L2_CHIP_MATCH_AC97</constant></entry> |
| 237 | <entry>3</entry> |
| 238 | <entry>Match the nth anciliary AC97 chip.</entry> |
| 239 | </row> |
| 240 | </tbody> |
| 241 | </tgroup> |
| 242 | </table> |
| 243 | </refsect1> |
| 244 | |
| 245 | <refsect1> |
| 246 | &return-value; |
| 247 | |
| 248 | <variablelist> |
| 249 | <varlistentry> |
| 250 | <term><errorcode>EINVAL</errorcode></term> |
| 251 | <listitem> |
| 252 | <para>The driver does not support this ioctl, or the kernel |
| 253 | was not compiled with the <constant>CONFIG_VIDEO_ADV_DEBUG</constant> |
| 254 | option, or the <structfield>match_type</structfield> is invalid, or the |
| 255 | selected chip or register does not exist.</para> |
| 256 | </listitem> |
| 257 | </varlistentry> |
| 258 | <varlistentry> |
| 259 | <term><errorcode>EPERM</errorcode></term> |
| 260 | <listitem> |
| 261 | <para>Insufficient permissions. Root privileges are required |
| 262 | to execute these ioctls.</para> |
| 263 | </listitem> |
| 264 | </varlistentry> |
| 265 | </variablelist> |
| 266 | </refsect1> |
| 267 | </refentry> |
| 268 | |
| 269 | <!-- |
| 270 | Local Variables: |
| 271 | mode: sgml |
| 272 | sgml-parent-document: "v4l2.sgml" |
| 273 | indent-tabs-mode: nil |
| 274 | End: |
| 275 | --> |